Nemesis: Martian Manhunter
Other Major Foes: Justice League of America
Appearances: 1 comic story
Powers: Inherent super strength, speed, and near invulnerability related to his large size (roughly fifty feet.) Ability to manifest additional powers upon contact with metahumans that allows him to exploit their weaknesses.
Korge is "the last angry god" of an alien world who handily defeated Martian Manhunter, Flash, Green Lantern, and Superman individually. However, the Atom came up with a plan that allowed the heroes to imprison Korge in a team effort.
Win: Rott (8-4)
Lose: Lobo (3-11); Brimstone
Nemesis: Wonder Woman
Other Major Foes: None
Appearances: 100+ comics, as well as cartoons, a video game, and live action television.
Powers: Inherent super strength and a degree of invulnerability related to her large size (up to 500 feet.)
The Golden Age Giganta was a gorilla evolved into a hulking homo-sapien female by Professor Zool. In more modern continuity, Dr. Doris Zeul is Giganta, prone to joining villainous collectives with her size-altering abilities.
I like Giganta, and she's one of the most iconic super-villainesses thanks to her time on Super Friends and later cartoons. A consequence of that is she's lost a lot of fights against plenty of lesser foes. After Wonder Woman, she's probably best known for battling shrinking metahumans like the Atom and Dwarfstar, which doesn't help her credibility. Korge's only appeared in one story, but he came off exceptionally well by owning many of DC's heaviest hitters. Giganta gets one punch, which could do serious damage, considering how much larger than Korge she can become. On the other hand, Giganta doesn't seem to ever get the job done with that first strike capability, and Korge's whole schtick is finding his opponent's Achilles heel after shaking off a first blow. Giganta has been brought low by considerably more diminutive offense.